Integrated circuit memory devices provided on an integrated circuit substrate are typically tested prior to assembly of the memory device. During this process, the integrated circuit memory devices may be classified as either good or bad. If a chip classified as bad malfunctions due to one or more failed cells, the failed cell(s) may be replaced by a redundant cell already included in the memory device. The repair process may include irradiating a laser-beam used to blow one or more fuses. Blowing the fuse(s) allows the redundant cell to have the same address as the failed cell in write/read modes. Generally, fuses are formed simultaneously with bit lines of the integrated circuit memory device. In other words, the fuses and the bit lines may be simultaneously formed using a single step of, for example, a photolithography/etching process. In some integrated circuit devices, the bit lines may be formed of a metal material such as tungsten in order to reduce the electrical resistance of the bit line. Thus, the fuses may also include a metal material.
Referring to FIGS. 1A and 1B, a top plan view illustrating a portion of a conventional fuse region and a cross section taken along the line I–I′ of FIG. 1A, respectively, will be discussed. A lower interlayer insulating layer 3 is provided on a surface of an integrated circuit substrate 1. A fuse 5 is provided on the lower interlayer insulating layer 3. The fuse 5 includes first and second parallel sub fuses 5a and 5b as well as a fuse connection 5c that connects a first end of the first sub fuse 5a to a first end of the second sub fuse 5b. The first and second sub fuses 5a and 5b and the fuse connection 5c may be formed by patterning a metal layer, such as a tungsten layer, using a single photolithography/etching process. As a result, the first and second sub fuses 5a and 5b and the fuse connection 5c may be formed of the same layer of metal. An upper interlayer insulating layer 7 is provided on the fuse 5. A second end of the first sub fuse 5a and a second end of the second sub fuse 5b are exposed by a first contact hole 7a and a second contact hole 7b, respectively, that penetrate the upper interlayer insulating layer 7, and the fuse connection 5c is exposed by a third contact hole 7c that penetrates the upper interlayer insulating layer 7.
A first contact plug 9a (FIG. 1), a second contact plug 9b, and a third contact plug 9c may be provided in the first, second, and third contact holes 7a, 7b, 7c, respectively. A first metal interconnect 11a, a second metal interconnect 11b and a third metal interconnect 11c are provided on the upper interlayer insulating layer 7. The first metal interconnect 11a is electrically coupled to the first contact plug 9a, and the second metal interconnect 11b is electrically coupled to the second contact plug 9b. In addition, the third metal interconnect 11c is electrically coupled to the third contact plug 9c. Thus, the first and third metal interconnects 11a and 11c are electrically coupled through the first sub fuse 5a, and the second and third metal interconnects 11b and 11c are electrically coupled through the second sub fuse 5b. A passivation layer 13 is provided on the first to third metal interconnects 11a, 11b and 11c. A fuse window 13a is provided inside the passivation layer 13 and the upper interlayer insulating layer 7. The fuse window 13a is provided on the first and second sub fuses 5a and 5b. An interlayer insulating layer 7t, which is thinner than the initial upper interlayer insulating layer 7, may be provided on the first and second sub fuses 5a and 5b. 
If one of the first and second sub fuses 5a and 5b, for example, the second sub fuse 5b is blown by, for example, a laser beam penetrating the fuse window 13a, during a repair process, the cut (blown) region of the second sub fuse 5b may be exposed to the atmosphere. After the repair process, the integrated circuit substrate including the fuse 5 may be encapsulated through an assembly process. However, the cut (blown) sub fuse 5b may be exposed to the moisture of the atmosphere or a subsequent wet process, such as a cleaning process, prior to the assembly process. Accordingly, the first sub fuse 5a may be corroded by moisture that may penetrate through the cut second sub fuse 5b and the fuse connection 5c. As a result, the first metal interconnect 11a may be electrically disconnected from the third metal interconnect 11c, which may cause the integrated circuit device to malfunction.
Furthermore, a laser beam used to blow (cut) tungsten fuses typically has higher energy than a laser beam used to blow polysilicon fuses or tungsten silicide fuses. As integrated circuit memory devices become more highly integrated, a pitch size of the fuses may also be reduced. Therefore, when a desired fuse is selectively blown, a non-selected fuse adjacent to the selected fuse may be damaged or cut due to the high energy laser beam and/or the smaller pitch size.
The damaged or cut tungsten fuse may be exposed to the atmosphere after the repair process. Thus, the damaged or cut tungsten fuse may be easily corroded due to moisture in the atmosphere, thereby possibly causing the integrated circuit device to malfunction. In particular, the tungsten layer may have a relatively strong oxidation characteristic relative to the polysilicon layer and the tungsten silicide layer. Hence, the damaged or cut tungsten fuse may lead to a remarkable reduction of a post-repair yield of an integrated circuit device.
A method of fabricating fuse regions that addresses some of the problems discussed above is provided in U.S. Pat. No. 5,618,750 to Fukuhara, et al. As stated therein, first, second and third interconnects are provided spaced apart on an integrated circuit substrate. The second and third interconnects are parallel to each other and are perpendicular to the first interconnects. The first to third interconnects are formed of a non-corrosive material layer. A first fuse is provided over a region between the first and second interconnects, and a second fuse is provided over a region between the first and third interconnects. First and second ends of the first fuse are electrically coupled to the first and second interconnects, respectively, and first and second ends of the second fuse are electrically coupled to the first and third interconnects, respectively. Accordingly, even if one of the fuses may be blown and moisture may penetrate through the blown region, the other fuse adjacent to the blown fuse may not be corroded due to the fact that the first interconnect includes a non-corrosive material layer. In other words, the first and third interconnects may act as corrosion stop layers.